Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 09-11-2020, 02:08 AM   #1 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Meausring lift

My 16 year old son has bought a car and, as the young often want to do, desires the largest rear wing available for it - the one fitted to the STi version.

His car is a 2002 Subaru Impreza RS, like this one:



Note that it already has a rear spoiler.

This is the wing he has bought:



It does appear to have an actual wing profile, and the end plates should act as fins, moving the lateral centre of pressure backwards.

This convinced me to donate $100 to the project, if I could aero test the car. The agreement was made, and so today I fitted a rear suspension height sensor to his car.

I use P38 Range Rover suspension height sensors - about 20 pounds (US$25) each on eBay UK.



Fitting is fiddly but not hard. I used two new 6mm balljoints (mine didn't come with the extra links). After this pic was taken, I slipped a piece of bike inner tube over the ball joints and link to keep the dust out.



I am using this circuit to smooth the output. It costs almost nothing and uses just a few passive components. The adjustment pot (being used as a variable resistor) adjusts the averaging time. It's needed to get an average ride height.



The 5V is supplied by a regulated cigarette socket phone charger and the signal is read by a multimeter.



I intend measuring rear ride height of the car with:
  • no rear spoiler
  • the small rear spoiler
  • the large wing

  Reply With Quote
The Following 3 Users Say Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020), California98Civic (09-17-2020), Gasoline Fumes (09-11-2020)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 09-11-2020, 06:25 AM   #2 (permalink)
Eco-ventor
 
jakobnev's Avatar
 
Join Date: Oct 2010
Location: sweden
Posts: 1,630

Princess - '92 Mazda MX-3 GS
House of Tudor
Team Mazda
90 day: 53.54 mpg (US)

Shirubāarō (*´ω`*) - '05 Toyota Prius Executive
Team Toyota
90 day: 54.88 mpg (US)

Blue Thunder - '20 Hyundai IONIQ Trend PHEV
Team Hyundai
Plug-in Hybrids
90 day: 587.16 mpg (US)
Thanks: 74
Thanked 701 Times in 444 Posts
Send a message via MSN to jakobnev
How about measuring the original spoiler with the (possibly) silly gap closed off?
__________________




2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)
  Reply With Quote
Old 09-11-2020, 06:03 PM   #3 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by jakobnev View Post
How about measuring the original spoiler with the (possibly) silly gap closed off?
This isn't to be a spoiler development exercise, but just the measurement of the rear lift/downforce with the car in three 'factory' configurations.

For the development of a rear spoiler, see:

  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020)
Old 09-11-2020, 09:22 PM   #4 (permalink)
Master EcoModder
 
Join Date: Aug 2018
Location: USA
Posts: 455

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)

Blueberry - '07 Toyota Camry SE
Thanks: 180
Thanked 101 Times in 77 Posts
Will you test mpg?

A lot of members would probably be interested in how much the spoilers affect fuel economy.
  Reply With Quote
Old 09-11-2020, 09:26 PM   #5 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by Taylor95 View Post
Will you test mpg?

A lot of members would probably be interested in how much the spoilers affect fuel economy.
Nope - no drag testing, no pressure testing, no tuft testing. He's not interested in any of those.
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020)
Old 09-11-2020, 11:27 PM   #6 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Measured rear ride height (sensor voltage) versus speed (km/h):

  Reply With Quote
The Following 4 Users Say Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020), California98Civic (09-17-2020), Gasoline Fumes (09-11-2020), Taylor95 (09-12-2020)
Old 09-12-2020, 03:13 AM   #7 (permalink)
Eco-ventor
 
jakobnev's Avatar
 
Join Date: Oct 2010
Location: sweden
Posts: 1,630

Princess - '92 Mazda MX-3 GS
House of Tudor
Team Mazda
90 day: 53.54 mpg (US)

Shirubāarō (*´ω`*) - '05 Toyota Prius Executive
Team Toyota
90 day: 54.88 mpg (US)

Blue Thunder - '20 Hyundai IONIQ Trend PHEV
Team Hyundai
Plug-in Hybrids
90 day: 587.16 mpg (US)
Thanks: 74
Thanked 701 Times in 444 Posts
Send a message via MSN to jakobnev
Overlaid:

Attached Thumbnails
Click image for larger version

Name:	overlay.png
Views:	148
Size:	28.1 KB
ID:	29126  
__________________




2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)
  Reply With Quote
The Following 2 Users Say Thank You to jakobnev For This Useful Post:
aerohead (09-16-2020), California98Civic (09-17-2020)
Old 09-12-2020, 03:33 AM   #8 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by jakobnev View Post
Overlaid:

Thanks.

Smoothing circuit (first time I have used this one) seemed to work well.
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020)
Old 09-12-2020, 03:54 AM   #9 (permalink)
Eco-ventor
 
jakobnev's Avatar
 
Join Date: Oct 2010
Location: sweden
Posts: 1,630

Princess - '92 Mazda MX-3 GS
House of Tudor
Team Mazda
90 day: 53.54 mpg (US)

Shirubāarō (*´ω`*) - '05 Toyota Prius Executive
Team Toyota
90 day: 54.88 mpg (US)

Blue Thunder - '20 Hyundai IONIQ Trend PHEV
Team Hyundai
Plug-in Hybrids
90 day: 587.16 mpg (US)
Thanks: 74
Thanked 701 Times in 444 Posts
Send a message via MSN to jakobnev
Quote:
This isn't to be a spoiler development exercise...
Shame, I was curious how much a gap like that is just marketing-wank.

Would you mind translating the voltages to force? (Just by lifting some weights in and out of the trunk)
__________________




2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)
  Reply With Quote
The Following User Says Thank You to jakobnev For This Useful Post:
aerohead (09-16-2020)
Old 09-12-2020, 04:29 AM   #10 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by jakobnev View Post
Shame, I was curious how much a gap like that is just marketing-wank.
I haven't done any measurement but I would think the boundary layer is so thick back there that the gap basically acts as if it isn't there. Here are some pics of a local car after driving on wet dirt roads that seems to support that idea of no / very low flow:






Quote:
Would you mind translating the voltages to force? (Just by lifting some weights in and out of the trunk)
I have done that extensively on my Insight (and all the data on this has already been published) but the damping and springs on the Impreza are too firm to easily do this statically.

I could do it dynamically (with weights in the boot) but to be honest, I can't be bothered.

The big wing provides downforce, and that's good enough for Alexander and me. All he wants to do now is finished sanding it back and painting it!

Basically, I hope this shows for all those people who spend all their time sitting behind a computer and arguing and guessing, how easy and cheap it is to measure real aero data...

Literally, about a day's work and under US$75...

(...and of course that measuring gear can be fitted to almost any car - you can use it for the rest of your life....)


Last edited by JulianEdgar; 09-12-2020 at 04:43 AM..
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
aerohead (09-16-2020)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com